For purifying waste water, for recovering water in the field of drinking water, or for cleaning and maintaining swimming pools, it is known to chlorinate the water. The use of chlorine is associated with certain disadvantages, however, such as skin and eye irritation and unpleasant odors.
It is also known to add hypochlorite to the water instead of chlorine, the sodium hypochlorite being produced by electrolysis from table salt.
Performing water treatment, disinfection and the like by means of ozone is also known, in which case the unpleasant side effects of chlorine do not occur. The generation of ozone from the oxygen component of air is effected by corona discharges with high voltage (for instance 15,000 volts), the generation of the high voltage being effected via single-phase air-cooled transformers.
It is also known to produce ozone by means of peak disharges. In these two last methods, the expenditure of energy is relatively high. The capital investment required for the electrical plant is correspondingly quite high.
It is further known, from U.S. Pat. No. 4,273,660, to purify water by the action of ultraviolet light and by ozone, where UV light is generated in a gas discharge lamp and O.sub.2 is converted into O.sub.3 with the aid of the UV light; the ozone is added to the water which is to be purified, and then the water-ozone mixture is in turn passed along the gas discharge lamp.